Data Sheet

95
Atmel | SMART SAM D21 [DATASHEET]
Atmel-42181G–SAM-D21_Datasheet–09/2015
14. GCLK – Generic Clock Controller
14.1 Overview
Several peripherals may require specific clock frequencies to operate correctly. The Generic Clock Controller consists of
number of generic clock generators and generic clock multiplexers that can provide a wide range of clock frequencies.
The generic clock generators can be set to use different external and internal clock sources. The selected clock can be
divided down in the generic clock generator. The outputs from the generic clock generators are used as clock sources for
the generic clock multiplexers, which select one of the sources to generate a generic clock (GCLK_PERIPHERAL), as
shown in Figure 14-2. The number of generic clocks, m, depends on how many peripherals the device has.
14.2 Features
z Provides generic clocks
z Wide frequency range
z Clock source for the generator can be changed on the fly
14.3 Block Diagram
The Generic Clock Controller can be seen in the clocking diagram, which is shown in Figure 14-1 .
Figure 14-1. Device Clocking Diagram
The Generic Clock Controller block diagram is shown in Figure 14-2.
GC
LK_I
O
G
eneric
C
lock
G
enerato
r
OSC
32K
OSC
ULP32K
XOSC
32
K
S
Y
SC
TRL
C
lock
D
ivider
&
Mas
k
er
C
loc
k
G
at
e
G
eneric Clock Multi
p
lexe
r
P
ERIPHERAL
S
G
ENERI
C
C
L
OC
K
CO
NTR
O
LLE
R
PM
GC
LK_MAI
N
D
FLL48M
X
OSC
OSC8M
FDPLL96M
GC
LK_PERIPHERA
L